Engine exhaust after-treatment system and method

ABSTRACT

Soot in engine exhaust gas is separated in a cyclonic filter and burned inside the cyclonic filter. An acoustic agglomerator has increased soot density in the engine exhaust gas before entering the cyclonic filter.

TECHNICAL FIELD

This disclosure relates to internal combustion engines, particularly to treatment of engine exhaust (sometimes referred to simply as after-treatment or exhaust after-treatment) in diesel engines which propel trucks, busses, motor coaches and similar large vehicles.

BACKGROUND OF THE DISCLOSURE

Combustion processes occurring within internal combustion engines create engine exhaust which passes through an exhaust system into surrounding atmosphere. Engine exhaust contains various products of combustion which include gases and particulate matter. One type of particulate matter is soot (black smoke) which may be generated when an engine idles and/or transitions from a lower to a higher power level.

Some products of combustion which are discharged into the atmosphere (tailpipe emissions) are subject to government regulation.

One known technology for reducing soot in tailpipe emissions from a diesel engine employs a diesel particulate filter (DPF) which traps soot. Trapped soot restricts exhaust flow, increasing exhaust backpressure on the engine which reduces engine output power and operating efficiency. Soot trapped in a DPF is burned off by a process called regeneration which is initiated when certain conditions are satisfied, such as once the soot's restriction of exhaust flow creates more than a defined engine backpressure.

SUMMARY OF THE DISCLOSURE

The disclosed after-treatment system comprises a cyclonic (vortex) filter into which engine exhaust is introduced. Exhaust flows in a vortex within an enclosure of the filter with unburned particulate matter separating from gases in the exhaust. The after-treatment system may further include an acoustic agglomerator for increasing density of unburned particulate matter prior to engine exhaust entering the cyclonic filter by causing soot particles to clump together.

A burner is associated with the cyclonic filter to deliver particulate-incinerating flow into the cyclonic filter. That flow incinerates unburned particulate matter into gases entraining with gases in exhaust detaching from the vortex within the enclosure of the cyclonic filter. The entrained gases exit the enclosure and pass out of the exhaust system through a tailpipe.

A general aspect of the disclosure relates to an internal combustion engine comprising an after-treatment system for treating exhaust gas coming from engine combustion chambers before passing into surrounding atmosphere. The after-treatment system comprises: a cyclonic filter for separating unburned particulate matter out of exhaust gas.

The cyclonic filter comprises an enclosure having a cylindrical sidewall extending longitudinally along an axis between a first end wall and a second end wall to enclose an interior space, an exhaust gas inlet through the sidewall to the interior space, and an exhaust gas outlet from the interior space through the first end wall.

The exhaust gas inlet directs exhaust gas into cyclonic flow (a vortex) which is circumscribed by the sidewall within the interior space and which carries unburned particulate matter toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the interior space through the exhaust gas outlet.

A first tube extends within the interior space from the second end wall coaxial with the sidewall.

A burner provides particulate-incinerating flow which enters, passes through, and exits the first tube.

A second tube is disposed within the interior space coaxially surrounding, and cooperating with, the first tube to cause particulate-incinerating flow exiting the first tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, the particulate-incinerating flow exiting the first tube and then out of the second tube to entrain with exhaust gas which has detached from the cyclonic flow.

Another general aspect of the disclosure relates to a method of treating exhaust gas coming from combustion chambers of an internal combustion engine before passing into surrounding atmosphere.

The method comprises: separating unburned particulate matter out of exhaust gas by directing exhaust gas through an exhaust gas inlet of a cyclonic filter having a sidewall extending between a first end wall and a second end wall and into cyclonic flow circumscribed by the sidewall to cause unburned particulate matter to move toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the cyclonic filter through an exhaust gas outlet in the first end wall; providing particulate-incinerating flow which enters, passes through, and exits a first tube inside the cyclonic filter and then enters a second tube inside the cyclonic filter; and causing particulate-incinerating flow exiting the first tube and entering the second tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, particulate-incinerating flow as the entrained flows pass through the second tube.

The foregoing summary, accompanied by further detail of the disclosure, will be presented in the Detailed Description below with reference to the following drawings that are part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side view of a truck vehicle.

FIG. 2 is a schematic diagram of a diesel engine that includes an after-treatment system.

FIG. 3 is a pictorial view of a first portion of the after-treatment system with a portion sectioned away to show an interior space of a portion of the system.

FIG. 4 is a longitudinal cross section view through a second portion of the after-treatment system associated with the first portion.

FIG. 5 is a view in the direction of arrows 5-5 in FIG. 4.

DETAILED DESCRIPTION

FIG. 1 shows a truck vehicle 10 having a chassis 12 and a cab body 14 supported on a frame of chassis 12 which also supports a fuel-consuming engine 16 of a powertrain 18. Engine 16 operates through a drivetrain of powertrain 18 to drive wheels 20 which propel the truck vehicle on land.

FIG. 2 shows engine 16 having an intake system 22 for conveying air to cylinders 24 within which fuel is combusted to operate the engine and an exhaust system 26 for conveying exhaust resulting from combustion in cylinders 24 to surrounding atmosphere. Exhaust system 26 includes an after-treatment system 28 for treating exhaust coming from cylinders 24 before passing into surrounding atmosphere.

Engine 16 is representative of a turbocharged diesel engine which propels truck vehicle 10 although other components associated with that type of engine are not shown in the drawing. Truck vehicle 10 is representative of a highway tractor, one type of large motor vehicle which is propelled by a diesel engine and which comprises a vertical tailpipe 30 through which treated exhaust is discharged into surrounding atmosphere.

FIGS. 3-5 show after-treatment system 28 to comprise at least a cyclonic filter 32 for separating unburned particulate matter out of exhaust gas, and a burner 34 for burning the separated particulate matter. System 28 may further include an acoustic agglomerator 36 for increasing density of unburned particulate matter in engine exhaust prior to entering cyclonic filter 32 by causing soot particles in the engine exhaust to clump together, rendering filter 32 more efficient.

In FIG. 3, cyclonic filter 32 is seen to comprise an enclosure 38 having a cylindrical sidewall 40 extending longitudinally along an axis 42 between a first end wall 44 and a second end wall 46 (shown only in FIG. 4) to enclose an interior space 48. Sidewall 40 is cylindrical except for a lower portion which has a frustoconical taper 47 in the direction away from first end wall 44. Exhaust which has passed through acoustic agglomerator 36 is introduced into cyclonic filter 32 through an exhaust gas inlet 50 and exits through an exhaust gas outlet 52 in first end wall 44.

Exhaust gas inlet 50 is open to interior space 48 through sidewall 40 immediately adjacent first end wall 44. Exhaust gas inlet 50 directs exhaust gas from acoustic agglomerator 36 into a cyclonic flow (a vortex 54) which is circumscribed within interior space 48 by sidewall 40. Vortex 54 carries unburned particulate matter toward second end wall 46 as exhaust gas detaches from the vortex as suggested by arrows 55 to flow out of interior space 48 through exhaust gas outlet 52. FIG. 4 shows only a portion of frustoconical taper 47 of sidewall 40, where second end wall 46 closes the narrow end of the taper.

A first tube 56 coaxial with sidewall 40 extends within interior space 48 from second end wall 46. A second tube 58, a third tube 60, and a fourth tube 62 are disposed within interior space 48 providing structure which defines a flow path for burning uncombusted particulate matter which has been separated by cyclonic filter 32 and for conveying gases created by burning of the particulate matter, as will be more fully explained hereinafter.

All tubes 56, 58, 60, 62 are mutually coaxial. Second tube 58 is supported by third tube 60 which in turn is supported by fourth tube 62. Tubes 58, 60, 62 are joined together in any suitably appropriate way such as at joints 64, 66 which are present in, but do not obstruct, the aforementioned flow path defined by those tubes. Tubes 58 and 62 are also joined at their lower ends as viewed in FIG. 4 by a ring 68 which has a radially inner wall 70 which forms a continuation of first tube 58 and a radially outer wall 72 which forms a continuation of fourth tube 62.

Radial clearance 74 is present between tubes 56 and 58. Ring 68 has radial clearance 76 to first tube 56, axial clearance 78 to second end wall 46, and radial clearance 80 to an upturned flange of second end wall 46 which joins with the narrow end of frustoconical taper 47. By acting as a continuation of first tube 58, radially inner wall 70 of ring 68 progressively increases radial clearance 76 from a minimum where it joins first tube 58 to a maximum at the lower end of ring 68.

Burner 34 provides particulate-incinerating flow, represented by arrows 82, which enters, passes through, and exits first tube 56. Clearances 74, 76, 78, 80 allow the particulate-incinerating flow 82 exiting first tube 56 to induce a flow of particulate matter which is being carried by the vortex toward second end wall 46. The flow passes through clearances 80, 78, 76 and 74 and into second tube 58 where it entrains with, and is incinerated by, the particulate-incinerating flow exiting first tube 56. The flow-inducing clearances are equivalent to having a venturi surrounding the exit end of first tube 56 which renders the flow out of first tube 56 effective to pull soot into second tube 58.

Gases created by burning of the particulate matter in the flow through second tube 58 are conveyed along a flow path indicated by arrows 84. The flow from second tube 58 passes through holes in an end wall 86 and reverses direction to then flow axially through radial clearance between second tube 58 and third tube 60 which may be considered to provide a first portion of a flow path structurally defined by tubes 58, 60. Upon exiting tube 60, the flow continues within the interior of ring 68 which reverses the flow direction so that the flow then continues through radial clearance between third tube 60 and fourth tube 62 which may be considered to provide a second portion of the flow path structurally defined by tubes 60, 62. Finally the flow passes out of the open end of fourth tube 62 and mixes within interior space 48 with the flow which has detached from the vortex and is moving axially toward exhaust gas outlet 52.

Burner 34 is constructed to impart swirl to the particulate-incinerating flow passing through first tube 56. Swirl promotes mixing of the entrained flows passing through second tube 58. Fuel is injected by an injector 88 into an airflow path 90 and ignited by an igniter 92 to create hot gas for incinerating unburned particulate matter. The hot gas is introduced tangentially into a swirl chamber 94 which is coaxial with an end of first tube 56 which is fit to a wall 96 of swirl chamber 92. Airflow path 90 is at a pressure at least as great as the pressure at exhaust gas outlet 52, and the hot gas for incinerating unburned particulate matter” is very lean, (i.e., oxygen rich). The possibility of supplemental air injection to ensure enough oxygen to convert all the carbon particulates to carbon dioxide is contemplated.

It is believed that a vortex filter/burner system as described, can, in comparison to a DPF, significantly reduce engine backpressure, resulting in increased engine power and efficiency. The burner may eliminate injections of excess fuel into engine cylinders which may occur in order to regenerate a DPF and the consequences of such injections on the engine. The disclosed system may also have favorable implications on other elements of an after-treatment system from the standpoints of performance, maintenance, and costs and may enable engine life to be increased. 

What is claimed is:
 1. An internal combustion engine comprising an after-treatment system for treating exhaust gas coming from engine combustion chambers before passing into surrounding atmosphere, wherein the after-treatment system comprises: a cyclonic filter for separating unburned particulate matter out of exhaust gas, the cyclonic filter comprising an enclosure having a cylindrical sidewall extending longitudinally along an axis between a first end wall and a second end wall to form an enclosure of an interior space, an exhaust gas inlet through the sidewall to the interior space, and an exhaust gas outlet from the interior space through the first end wall; the exhaust gas inlet directing exhaust gas into cyclonic flow circumscribed by the sidewall within the interior space and carrying unburned particulate matter toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the interior space through the exhaust gas outlet; a first tube which extends within the interior space from the second end wall coaxial with the sidewall; a burner providing particulate-incinerating flow which enters, passes through, and exits the first tube; and a second tube disposed within the interior space coaxially surrounding, and cooperating with, the first tube to cause particulate-incinerating flow exiting the first tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, particulate-incinerating flow exiting the first tube and then out of the second tube.
 2. An engine as set forth in claim 1 further comprising structure defining a flow path for conveying flow out of the second tube for entrainment with exhaust gas which has detached from the cyclonic flow.
 3. An engine as set forth in claim 2 in which the structure opens within the interior space to cause the entrainment of flow out of the second tube with exhaust gas which has detached from the cyclonic flow to occur within the interior space.
 4. An engine as set forth in claim 3 in which the structure comprises a third tube which cooperates with the second tube to form a first portion of the flow path by radial clearance between the second tube and the third tube, and third tube which cooperates with a fourth tube to form a second portion of the flow path by radial clearance between the third tube and the fourth tube.
 5. An engine as set forth in claim 1 in which the burner is constructed to impart swirl to the particulate-incinerating flow passing through first tube.
 6. An engine as set forth in claim 1 including an acoustic agglomerator for increasing density of unburned particulate matter in exhaust gas prior to exhaust gas entering the cyclonic filter.
 7. A method of treating exhaust gas coming from combustion chambers of an internal combustion engine before passing into surrounding atmosphere, the method comprising: separating unburned particulate matter out of exhaust gas by directing exhaust gas through an exhaust gas inlet of a cyclonic filter having a sidewall extending between a first end wall and a second end wall and into cyclonic flow circumscribed by the sidewall to cause unburned particulate matter to move toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the cyclonic filter through an exhaust gas outlet in the first end wall; providing particulate-incinerating flow which enters, passes through, and exits a first tube inside the cyclonic filter and then enters a second tube inside the cyclonic filter; and causing particulate-incinerating flow exiting the first tube and entering the second tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, particulate-incinerating flow as the entrained flows pass through the second tube.
 8. A method as set forth in claim 7 further comprising defining a flow path inside the cyclonic filter for conveying the entrained flows out of the second tube and into entrainment with exhaust gas which has detached from the cyclonic flow.
 9. A method as set forth in claim 7 comprising imparting swirl to the particulate-incinerating flow.
 10. A method as set forth in claim 7 including increasing density of unburned particulate matter in exhaust gas prior to exhaust gas entering the cyclonic filter. 